1. Field of the Invention
The present invention relates to an image processing technique.
2. Description of the Related Art
Techniques for detecting the edge of a line or text for an inputted image are known. Also, in Japanese Patent Laid-Open No. H11-55503, an image processing apparatus that performs an image process (outline processing, or the like) for enhancing a reproducibility of an edge for a pixel which is determined to be on an edge of a line or text in the case of edge detection is disclosed.
Also, there are cases in which a white gap appears between colors of a color print material that are printed on a print medium such as a sheet upon image printing in an image forming apparatus such as a color printing device, and a portion for which a particular color is noticeable, i.e. a “misregistration” occurs. In response to this, in Japanese Patent Laid-Open No. 2007-36699, an image processing apparatus that detects a boundary of colors for an inputted image, and performs trapping processing for preventing an unprinted portion due to a misregistration for a pixel determined to be at a location at which the misregistration could occur has been proposed.
However, there are cases in which image processing for enhancing the reproducibility of an edge should not be performed even for a pixel that is determined to be on an edge of a line or text. An example of this is an edge in an image such as a semi-transparent object which is an object for which a transmittance is set. Specifically, a semi-transparent object is generated as a semi-transparency pattern image for which pixels are thinned in a pattern form in accordance with a transmittance for an object which has normal color values. Thus, a region of a semi-transparency pattern image is determined to be an edge of a line or text, and the image processing for enhancing the reproducibility of the edge is performed. Thus an increase in a density, a change in a color value, or the like, for the pixel occurs due to the outline processing, and a color value becomes denser, and a color becomes different for the image than what it would be if the image were reproduced as it originally should have been.
Also, similarly, when a color boundary detection is performed for a semi-transparency pattern image, a region of the semi-transparency pattern image is determined to be a location at which a misregistration could occur, and trapping processing is performed. Consequently, the color of the semi-transparency pattern is trapped in a text portion, or a color of text is trapped in a semi-transparency pattern portion, and an image having a different color is obtained.